54 



SEX-LINKED INHERITANCE IN DROSOPHILA. 



point at which in normal flies the anterior cross-vein lies. The cross- 

 vein and the cell normally cut off by it are absent. There are a number 

 of other features (see fig. D c) characteristic of this mutation: the wings 

 are held out at a wide angle from the body, the ocelli are very much 

 reduced in size or entirely absent, the bristles around the ocelli are 

 usually small. The females are absolutely sterile, not only with their 

 own, but with any males. 



Fused males by wild females gave wild-type males and females. 

 Inbred these gave the results shown in table 32. The fused character 

 reappeared only in the Fo males, showing that it is a recessive sex- 

 linked character. 



Table 32.— Pi fused & X zvild 9 9 . 



The reciprocal cross was tried many times, but is impossible, owing 

 to the sterility of the females. Since the fused females are sterile to 

 fused males, the stock is kept up by breeding heterozygous females to 

 fused males. 



By means of the following experiments the position of fused in the 

 X chromosome was determined. A preliminary test was made by 

 mating with eosin, whose factor lies near the left end of the X chromo- 

 some series. 



LINKAGE OF EOSIN AND FUSED. 



Fused (red-eyed) males mated to eosin (not-fused) females gave wild- 

 type daughters and eosin sons, which inbred gave the classes shown in 

 table 33. 



Table 33. — Pj eosin 9 9 X fused cf cf . Fj tvild-type 9 9 X Fi eosin cf cT- 



